Automatic sheet feeding device in printing machine

ABSTRACT

An automatic feeding device in a printing machine includes: a sheet container containing a number of sheets, a pick-up unit picking up and transporting sheets in the sheet container using a rotational friction, a driving unit driving the pick-up unit, and at least one sheet separator roller rotatably installed in a transport path of the sheets to rotate in a direction opposite to a sheet transport direction to individually separate the sheets one by one picked up by the pick-up unit. The sheet separator rollers rotate in response to a driving force of the driving unit and frictionally contact the picked sheets to separate the sheets one by one. According to the automatic feeding device, when the sheets are fed, the sheet separator rollers rotate in the direction opposite to the sheet transport direction and frictionally contact leading ends of the sheets to separate the sheets so that the sheets can be always separated in a reliable manner regardless of deformation or a type of the sheets.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Korean Patent Application No. 2002-38692, filed Jul. 4, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an automatic sheet feeding device in a printing machine, such as an ink jet printer and a multi-function machine, and more particularly, to an automatic sheet feeding device able to prevent an overlapped transport, in which at least two printing sheets are transported as overlapped, (hereinafter it will be referred to as ‘overlapped transport’) and a skew of the printing sheets in the printing machine.

[0004] 2. Description of the Related Art

[0005] As is well known in the art, an automatic sheet feeding device feeding sheets in a printing machine has a sheet separating structure for the purpose of preventing overlapped feeding.

[0006]FIGS. 1A to 3 illustrate a general automatic feeding device in a printing machine having a sheet container 10 receiving a number of sheets P, a pick-up unit 20, a driving unit 30, and a claw 80 separating the sheets P one by one.

[0007] As shown in FIGS. 1A, 1B and 2, the sheet container 10 has a rear plate 11, side plates 12 and 12′ extended forward from both sides of the rear plate 11, and a bottom plate 13 extended forward from a lower portion of the rear plate 11 at a given angle. The bottom plate 13 has a number of dam frictions 13 a.

[0008] The pick-up unit 20 picks up one of the sheets P loaded in the sheet container 10 to transport the same, and have a press plate 21, a pick-up shaft 22, and a pair of pick-up rollers 23 and 23′.

[0009] As shown in FIG. 2, the press plate 21 is installed on the rear plate 11 of the sheet container 10 to pivot around an upper portion of the rear plate 11. A lower portion of the press plate 21 is elastically supported against the pick-up shaft 22 by a spring 24 disposed between the rear plate 11 and the press plate 21.

[0010] The pick-up shaft 22 is rotatably installed in the side plates 12 and 12′ of the sheet container 10 and rotationally driven by the driving unit 30.

[0011] The pick-up rollers 23 and 23′ are mounted on the pick-up shaft 22, spaced-apart by a proper distance, and rotated together with the pick-up shaft 22 in a direction for transporting the sheets P.

[0012] The sheets P loaded in the sheet container 10 are applied with a certain amount of pressure by the press plate 21 between the press plate 21 and the pick-up rollers 23 and 23′ rotating to pick up and transport one sheet owing to a frictional force of thereof.

[0013] The driving unit 30 has a motor 31 functioning as a driving source and a gear train 32 transporting a driving force of the motor 31 to the pick-up shaft 22. As the motor 31 is driven, the driving force is transferred to the pick-shaft 22 via the gear train 32 to rotationally drive the pick-up rollers 23 and 23′.

[0014] As shown in FIGS. 1 B and 3, the claw 40 is disposed in a position of the bottom plate 13 of the sheet container 10 to contact a corner of a leading end of one of the sheets P. This helps the claw 40 apply a proper amount of a frictional force to the sheets P which are picked up and transported by the pick-up rollers 23 and 23′. Where two sheets are picked up, the claw 40 applies the frictional force to a lower one overlapped with an upper one to stop the upper one from being transported.

[0015] The automatic feeding device includes a sheet guide 50 aligning the sheets P in the sheet container 10 according to a sheet size of the sheets P, which are mounted on the sheet guide 10 in a longitudinally movably manner.

[0016] However, in the general automatic feeding device in the printing machine as described above, when the sheets P are contained and loaded in the sheet container 10 for a long time period to be deformed therein, the claw 40 may fail to separate the sheets P, and the sheets P are transported as overlapped with another sheet of which a leading end is released from the claw 40.

[0017] Further, in the conventional automatic feeding device, the claw 40 separating sheets P is installed only in one side so that an unbalanced pick-up force is generated during pick-up of the sheets P to result in so-called skew where the sheets P are fed as inclined. Such a sheet skew also affects a printing process to cause a printing defect on a printing image and thus requires improvement.

[0018] Moreover, where a thick sheet is used, the conventional automatic feeding device may fail to pick up the sheet since one leading end of the sheet contacts the claw 40 requiring a relatively large amount of a pick-up force. That is, although pick-up conditions are different owing to a sheet thickness, the claw 40 carries out sheet separation in the same condition regardless of a sheet type, thereby failing to properly cope with a different sheet type.

SUMMARY OF THE INVENTION

[0019] The present invention has been made to solve the foregoing and/or other problems, and it is therefore an aspect of the present invention to provide an automatic feeding device in a printing machine which can stably separate sheets regardless of deformation or sheet type of contained sheets to prevent overlapped transport of the sheets.

[0020] It is another aspect of the invention to provide an automatic feeding device in a printing machine which can uniformly apply a pick-up force to picked-up sheets to prevent a skew of the picked-up sheets.

[0021] Additional aspects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

[0022] According to an aspect of the invention to obtain the above and/or other aspects, an automatic feeding device in a printing machine is provided which includes a sheet container containing a number of sheets, a pick-up unit picking up and transporting the sheets contained in the sheet container using a rotational friction, a driving unit driving the pick-up unit, and at least one sheet separator roller rotatably installed in a transport path of the sheets to rotate in a direction opposite to that of the sheet transport path to individually separate the sheets picked up by the pick-up unit.

[0023] The automatic feeding device may comprise two sheet separator rollers disposed to be spaced-apart from each other by a proper distance, wherein the sheet separator rollers rotate in response to a driving force received from the driving unit.

[0024] According to another aspect of the automatic feeding device, when the sheets are fed, the sheet separator rollers rotate in a direction opposite to that of the sheet transport path and frictionally contact leading ends of the sheets to separate the sheets so that the sheets can be always separated in a reliable manner regardless of deformation or a type of the sheets.

[0025] The sheet container has a rear plate, side plates extended forward from both sides of the rear plate, and a bottom plate extended forward from a lower portion of the rear plate at a given angle and having a number of dam frictions, and wherein the sheet separator rollers each are mounted on an underside of the bottom plate and have a portion projecting from the rear plate by a proper height.

[0026] It is possible that the height is about 0.5 to 2.0 mm.

[0027] The sheet separator rollers are made of a material having a frictional force larger than that of the dam frictions, and in particular, the sheet separator rollers are made of an elastic material enabling a smooth pick-up of the sheets regardless of their thickness.

[0028] It is possible that the sheet separator rollers each have a number of protrusions in an outer peripheral surface.

[0029] Further, the sheet separator rollers can be installed in a single shaft with a given distance. Alternatively, the sheet separator rollers can be individually coupled with separate first and second shafts to receive a driving force from the driving unit. It is possible that the sheet separator rollers are constructed to rotate under the driving force received from driving means.

[0030] Where a single shaft is provided between the sheet separator rollers and the driving unit, the driving unit includes a motor functioning as a driving source, a gear train transferring the driving force from the motor to the pick-up unit and a driving force relay gear coupled with the shaft engaging the gear train.

[0031] Where the two first and second shafts are provided between the sheet separator rollers and the driving unit, the driving unit include the motor functioning as the driving source, the gear train transferring the driving force from the motor to the pick-up unit, a driving force relay gear coupled with the first shaft engaging the gear train, and a second gear train transferring the driving force from the pick-up unit to the second shaft.

[0032] The pick-up unit includes a pick-up shaft rotatably supported by the side plates of the sheet container, a pair of pick-up rollers coupled with the pick-up shaft and spaced-apart from each other by a proper distance, and a press plate installed in the rear plate of the sheet container to pivot around its upper portion and having a lower portion being elastically supported against the pick-up shaft by a spring which is interposed between the rear plate and the press plate.

[0033] In addition, the automatic feeding device of the invention may comprise a sheet guide installed in the sheet container in a longitudinally movable manner to align the sheets in the sheet container according to a size of the sheets in use.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and/or other aspects, features and other advantages of the present invention will become apparent and more readily appreciated from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0035]FIGS. 1A and 1B are schematic perspective views of a conventional automatic feeding device in a printing machine;

[0036]FIG. 2 is a sectional view showing a feeding operation in the conventional automatic feeding device in the printing machine shown in FIGS. 1A and 1 B;

[0037]FIG. 3 is a detailed plan view showing a contact state between a claw and a sheet in the conventional feeding device shown in FIGS. 1A and 1 B; and

[0038]FIGS. 4A and 4B are schematic perspective view of an automatic feeding device according to an embodiment of the invention;

[0039]FIG. 5 is a sectional view showing a feeding operation in the automatic feeding device shown in FIGS. 4A and 4B; and

[0040]FIG. 6 is a sectional view of a sheet separator roller of the automatic feeding device shown in FIGS. 4A and 4B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described in order to explain the present invention by referring to the figures.

[0042] As shown in FIGS. 4A to 5, an automatic feeding device according to an embodiment of the present invention has a sheet container 10, a pick-up unit 20, a driving unit 30, and sheet separator rollers 100.

[0043] The sheet container 10 has a rear plate 11, side plates 12 and 12′ extended forward from both sides of the rear plate 11, and a bottom plate 13 extended forward from a lower portion of the rear plate 11 at a given angle. The bottom plate 13 has a number of dam frictions 13 a.

[0044] The pick-up unit 20 picks up one of sheets P loaded in the sheet container 10 to transport the same, and has a press plate 21, a pick-up shaft 22 and a pair of pick-up rollers 23 and 23′.

[0045] As shown in FIG. 5, the press plate 21 is installed in the rear plate 11 of the sheet container 10 to pivot around an upper portion of the rear plate 11. A lower portion of the press plate 21 is elastically supported against the pick-up shaft 22 by a spring 24 disposed between the rear plate 11 and the press plate 21.

[0046] The pick-up shaft 22 is rotatably installed in the side plates 12 and 12′ of the sheet container 10 and rotationally driven by the driving unit 30.

[0047] The sheets P loaded in the sheet container 10 are applied with a certain amount of pressure by the press plate 21 between the press plate 21 and the pick-up rollers 23 and 23′, which are rotated to pick up and transport one sheet owing to a frictional force of thereof.

[0048] The driving unit 30 has a motor 31 functioning as a driving source and a gear train 32 to transmit a driving force of the motor 31 to the pick-up shaft 22. As the motor 31 is driven, the driving force is transferred to the pick-shaft 22 via the gear train 32 to rotationally drive the pick-up rollers 23 and 23′. The driving unit 30 have the sheet separator rollers 100 according to a characteristic of the invention, which are rotated in a direction opposite to a sheet transport direction of the pick-up rollers 23 and 23′.

[0049] The sheet separator rollers 100 each is rotatably mounted on a bottom side of the bottom plate 13 of the sheet container 10 and has a portion thereof projecting from the bottom plate 13 by a proper height h. The sheet separator rollers 100 receive the driving force from the driving unit 30 to rotate in the direction opposite to the sheet transport direction of the pick-up unit 20. This causes the sheet separator rollers 100 to frictionally contact a leading end of the sheet P which is picked up and transported by the pick-up unit 20. Where two sheets are picked up, only one sheet is fed and the other one is stopped. In this case, the height h is preferably about 0.5 to 2.0 mm.

[0050] As shown in FIGS. 4A and 4B, the sheet separator rollers 100 are disposed under the bottom plate 13 and coupled with one ends of first and second shafts 110 and 120 which are rotatably and respectively supported to the side plates 12 and 12′ of the sheet container 10. Force relay gears 111 and 121 are respectively coupled with the other ends of the first and second shafts 110 and 120. The force relay gear 111 engages the gear train 32 and the force relay gear 121 engages a second gear train 130 so that the driving force transferred to the pick-up shaft 22 from the driving unit 30 is transferred to the force relay gear 121. This allows the two sheet separator rollers 100 to be rotated in a feeding operation.

[0051] The sheet separator rollers 100 are made of a material having a frictional force larger than that of the dam frictions 13 a which are provided in the bottom plate 13 of the sheet container 10. For example, the sheet separator rollers 100 can be made of rubber having a certain degree of elasticity. Where an excessive pressure is applied to leading ends of sheets P according to a sheet type, the sheet separator rollers 100 receive a pressure from the sheets P while uniformly maintaining the pick-up force so that the sheets P can be smoothly picked up regardless of their thickness.

[0052] Further, as shown in FIG. 6, the sheet separator rollers 100 each have an indented portion 100 a in an outer peripheral surface.

[0053] Although the shown embodiment describes that the sheet separator rollers 100 are respectively coupled with the first and second shafts 110 and 120, the sheet separators 100 can be coupled at a given distance with one shaft which is rotatably supported to the side plates 12 and 12′ of the sheet container 10. This construction provides only a portion of the shaft with only one force relay gear which engages the gear train 32 of the driving unit 30.

[0054] Hereinafter it will be described about a feeding operation of the automatic feeding device in a printing machine of the invention having the above construction.

[0055] A number of sheets P are loaded between the press plate 21 and the pick-up rollers 23 and 23′ which are installed in the sheet container 10. The sheet guide 50 is moved to a proper position in the sheet container 10 according to a sheet size. The leading ends of the sheets P contact the sheet separator rollers 100 which project from the bottom plate 13. Therefore, the sheets P do not slip down to be maintained in a stably loaded state even if they are contained in the sheet container 10 for a long time period.

[0056] When a printing or copy signal is inputted in a loaded state of the sheets P as above, the motor 31 is driven to transfer the driving force to the pick-up shaft 22 via the gear train 32 so that the pick-up rollers 23 and 23′ are rotated to pick up and transport the sheets P. The driving force of the motor 31 is also transferred via the force relay gears 111 and 121 and the second gear train 130 to the shafts 110 and 120 of the sheet separator rollers 100, respectively, so that the sheet separator rollers 100 rotate in the direction opposite to the sheet transport direction.

[0057] Where two sheets are picked up, the leading ends of the sheets frictionally contact with the sheet separator rollers 100. Only one of the sheets is normally fed, and the other overlapped sheet is not transported but stopped by the sheet separator rollers 100. The sheet separator rollers 100 reliably carry out a sheet separating operation regardless of deformation of the sheet P or sheet type of the sheet P. Also the pick-up force is applied to the sheet P as the leading ends of the sheets P are supported by the two sheet separator rollers 100 so as to prevent a skew of the sheets P.

[0058] According to the invention as set forth above, the sheets are separated by the sheet separator rollers rotating in a direction opposite to the sheet transport direction so that sheet separation is always carried out in a reliable manner regardless of deformation of a sheet or a sheet type. Accordingly, this can eliminate a sheet loss or a consumer dissatisfaction owing to an overlapped transport of the sheets.

[0059] Furthermore, according to the invention, the two sheet separator rollers are installed in the bottom plate of the sheet container so that the sheets of the sheet container contact the sheet separator rollers. This ensures that the sheets in the sheet container contact the sheet separator rollers to maintain a stable sheet containing state, in which the sheets do not slip down even though they are contained for a long time period. Also the pick-up rollers equivalently apply the pick-up force to the both sides of the sheets preventing the skew of the sheets.

[0060] While this invention has been shown and described in connection with the preferred embodiment for illustrating the principle of the present invention, the present invention is not limited to the construction and operation just the way as it is shown and disclosed as such. Rather, it is to be understood to those skilled in the art that it is possible to do various modifications and variations to the present invention without departing the spirit and scope of the appended claims and their equivalents. Therefore, those appropriate modifications and variations and equivalents should be considered to be within the scope of the present invention. 

What is claimed is:
 1. An automatic feeding device in a printing machine, comprising: a sheet container containing a number of sheets; a pick-up unit picking up and transporting the sheets from the sheet container using a rotational friction; a driving unit driving the pick-up unit; and a sheet separator roller rotatably installed in a transport path of the sheets to rotate in a direction opposite to a sheet transport direction to individually separate the sheets picked up by the pick-up unit.
 2. The automatic feeding device according to claim 1, wherein the sheet separator roller comprises: first and second sheet separator rollers disposed to be spaced-apart from each other by a distance and to rotate in response to a driving force received from the driving unit.
 3. The automatic feeding device according to claim 2, wherein the sheet container comprises a rear plate, side plates extended from both sides of the rear plate, and a bottom plate extended from a lower portion of the rear plate at a given angle and having a number of dam frictions, and the first and second sheet separator rollers each is mounted on a side of the bottom plate and comprises a portion thereof projecting from the bottom plate by a height.
 4. The automatic feeding device according to claim 3, wherein the height is 0.5 to 2.0 mm inclusive.
 5. The automatic feeding device according to claim 3, wherein the first and second sheet separator rollers are made of a material having a frictional force larger than that of the dam frictions.
 6. The automatic feeding device according to claim 5, wherein the first and second sheet separator rollers are made of an elastic material.
 7. The automatic feeding device according to claim 6, wherein the sheet separator rollers each have a number of protrusions at an outer peripheral surface.
 8. The automatic feeding device according to claim 3, further comprising: one shaft supported to the side plates of the sheet container and rotating in response to the driving force of the driving unit, wherein the first and second sheet separator rollers are installed on the shaft.
 9. The automatic feeding device according to claim 8, wherein the driving unit comprises: a motor functioning as a driving source; a gear train transferring the driving force from the motor to the pick-up unit; and a driving force relay gear coupled with the shaft to engage the gear train.
 10. The automatic feeding device according to claim 3, the shaft comprises: first and second shafts which are respectively supported to the side plates of the sheet container and rotating in response to the driving force of the driving unit, wherein the first and second sheet separator rollers are respectively coupled with the first and second shafts.
 11. The automatic feeding device according to claim 10, wherein the driving unit comprises: a motor functioning as a driving source; a gear train transferring the driving force from the motor to the pick-up unit; a driving force relay gear coupled with the first shaft to engage the gear train; and a second gear train transferring the driving force from the pick-up unit to the second shaft.
 12. The automatic feeding device according to claim 3, wherein the pick-up unit comprises: a pick-up shaft rotatably supported by the side plates of the sheet container; a pair of pick-up rollers coupled with the pick-up shaft; a press plate installed on the rear plate of the sheet container to pivot around an upper portion of the rear plate and having a lower portion being elastically supported against the pick-up shaft; and a spring disposed between the rear plate and the press plate.
 13. The automatic feeding device according to claim 3, further comprising: a sheet guide installed in the sheet container in a longitudinally movable manner to align the sheets in the sheet container according to a size of the sheets in use.
 14. An automatic feeding device in a printing machine, comprising: a sheet container containing a number of sheets; a driving unit generating a driving force; a pick-up unit picking up and transporting the sheets toward a transport path in a transport direction in response to the driving force of the driving unit; and a sheet separator roller disposed on the transport path of the sheets, contacting leading ends of the sheets, and rotating in response to the driving force of the driving unit to separate the sheets one by one.
 15. The automatic feeding device according to claim 14, wherein the sheet separator roller rotates in a direction opposite to the transport direction of the sheets.
 16. The automatic feeding device according to claim 14, wherein the pick-up unit comprises a pick-up roller rotating in a first rotational direction to pick-up and transport the sheets through the transport path in the transport direction, and the sheet separator roller rotates in a second rotational direction opposite to the first rotational direction of the pick-up roller.
 17. The automatic feeding device according to claim 14, further comprising: another sheet separator roller wherein the sheet separator roller and another sheet separator roller are disposed in a direction perpendicular to the transport direction to contact the leading ends of the sheets.
 18. The automatic feeding device according to claim 14, wherein the driving unit comprises: a gear train transmitting the driving force to the pick-up unit and the sheet separator roller.
 19. The automatic feeding device according to claim 14, wherein the driving unit comprises: a gear train transmitting the driving force to the pick-up unit; and a driving force relay gear transmitting the driving force to the sheet separating roller.
 20. The automatic feeding device according to claim 14, wherein the sheet container comprises: a plate disposed on the transport path to guide the sheets in the transport direction when the sheets are picked-up by the pick-up unit, wherein the sheet separator roller is rotatably disposed on the plate.
 21. The automatic feeding device according to claim 20, wherein the sheet separator roller comprises: a portion protruding from a surface of the plate to contact the leading ends of the sheets.
 22. The automatic feeding device according to claim 21, wherein the plate comprises: an opening through which the portion of the sheet separator roller protrudes toward the transport path of the sheets.
 23. The automatic feeding device according to claim 21, further comprising: a shaft disposed on the plate opposite to the transport path to be coupled between the sheet separator roller and the driving unit.
 24. The automatic feeding device according to claim 23, further comprising: a driving force relay gear formed on a first end of the shaft to receive the driving force, wherein the sheet separator roller is coupled on a second end of the shaft.
 25. The automatic feeding device according to claim 21, wherein the portion of the sheet separator roller comprises: protrusions formed on an outer peripheral surface of the portion.
 26. The automatic feeding device according to claim 25, wherein the protrusions of the portion are disposed in a direction perpendicular to the transport path.
 27. The automatic feeding device according to claim 25, wherein the protrusions of the portion are disposed between the leading ends of the sheets.
 28. The automatic feeding device according to claim 21, wherein the portion of the sheet separator roller comprises: grooves formed on an outer peripheral surface to receive corresponding ones of the leading ends of the sheets when the sheets are picked-up by the pick-up units.
 29. An automatic feeding device in a printing machine, comprising: a sheet container containing a number of sheets; a pick-up unit picking-up and transport the sheets toward a transport path in a transport direction; and a sheet separator roller disposed on the transport path of the sheets, and rotating in a direction opposite to the transport direction to separate the sheets one by one.
 30. The automatic feeding device according to claim 29, further comprising: a driving unit generating a driving force, wherein the pick-up unit and the sheet separator roller rotate in response to driving force of the driving unit.
 31. An automatic feeding device in a printing machine, comprising: a sheet container containing a number of sheets and having a bottom plate to support the sheets; a pick-up unit rotating to pick up and transport the sheets toward a transport path in a transport direction; and two sheet separator rollers installed in the bottom plate of the sheet container so that the sheet separator rollers contact the sheets of the sheet container to separate the sheets one by one. 